This invention relates generally to metal-clad switchgear and, more particularly, to self-cooling of the primary disconnecting contacts and current transformers for removable circuit breaker units in metal-clad switchgear.
The primary disconnecting contacts for drawout circuit breaker units are usually disposed inside of bushings when the switchgear is utilized in relatively high voltage systems. Surrounding the bushings, and therefore, the primary contacts, are current transformers which are utilized to monitor the current flow through the contacts. The supports for the current transformers usually surround and enclose the current transformers and the bushings and contacts disposed therein. However, a problem arises when the amount of current flowing through the contacts becomes relatively large. The current flowing through the contacts causes the contacts to heat. At the same time, the current transformers also heat. This causes a temperature rise within the enclosure formed by the current transformers support, which temperature rise, for safety reasons, must be minimized.
One method utilized in the prior art to limit the temperature rise was the use of forced cooling by means of fans and blowers to cool the current transformers and primary disconnecting contacts. This use of blowers and fans has drawbacks, however, in that it was not always possible to provide adequate cooling of the current transformers, and also in that space and energy must be utilized to install and operate the fans and blowers.